`tsconfig` Templates

Every package should get its own copy of the three files in this directory and the one in test/ (which should go in an analogous spot in the package). Package-specific options should go in tsconfig.json and test-specific options in tsconfig.test.json. The types file shouldn't need to be modified, and only exists because tsconfigs don't support multiple inheritence. The same goes for the file in test/, which only exists because VSCode only knows to look for a file named (exactly) tsconfig.json.